netdev - Re: [PATCH net-next 0/4] net: rps/rfs improvements

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Message-ID: <16988771.uLZWGnKmhe@eq59>
Date:   Wed, 29 Mar 2023 21:17:06 +0800
From:   Aiden Leong <aiden.leong@...sd.com>
To:     edumazet@...gle.com
Cc:     davem@...emloft.net, eric.dumazet@...il.com,
        kernelxing@...cent.com, kuba@...nel.org, netdev@...r.kernel.org,
        pabeni@...hat.com
Subject: Re: [PATCH net-next 0/4] net: rps/rfs improvements

Hi Eric,

I hope my email is not too off-topic but I have some confusion on how 
maintainers and should react to other people's work.

In short, you are stealing Jason's idea&&work by rewriting your implementation 
which not that ethical. Since your patch is based on his work, but you only 
sign-off it by your name, it's possible to raise lawsuit between Tencent and 
Linux community or Google.

I'm here to provoke a conflict because we know your name in this area and I'd 
to show my respect to you but I do have this kind of confusion in my mind and 
wish you could explain about it.

There's another story you or Tom Herbert may be interested in: I was working 
on Foo Over UDP and have implemented the missing features in the previous 
company I worked for. The proposal to contribute to the upstream community was 
rejected later by our boss for unhappy events very similar to this one.

Aiden Leong

> Jason Xing attempted to optimize napi_schedule_rps() by avoiding
> unneeded NET_RX_SOFTIRQ raises: [1], [2]
> 
> This is quite complex to implement properly. I chose to implement
> the idea, and added a similar optimization in ____napi_schedule()
> 
> Overall, in an intensive RPC workload, with 32 TX/RX queues with RFS
> I was able to observe a ~10% reduction of NET_RX_SOFTIRQ
> invocations.
> 
> While this had no impact on throughput or cpu costs on this synthetic
> benchmark, we know that firing NET_RX_SOFTIRQ from softirq handler
> can force __do_softirq() to wakeup ksoftirqd when need_resched() is true.
> This can have a latency impact on stressed hosts.
> 
> [1] https://lore.kernel.org/lkml/20230325152417.5403-1-> 
kerneljasonxing@...il.com/
> [2] https://lore.kernel.org/netdev/20230328142112.12493-1-kerneljasonxing@gmail.com/
> 
> 
> Eric Dumazet (4):
>   net: napi_schedule_rps() cleanup
>   net: add softnet_data.in_net_rx_action
>   net: optimize napi_schedule_rps()
>   net: optimize ____napi_schedule() to avoid extra NET_RX_SOFTIRQ
> 
>  include/linux/netdevice.h |  1 +
>  net/core/dev.c            | 46 ++++++++++++++++++++++++++++++---------
>  2 files changed, 37 insertions(+), 10 deletions(-)

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